Question

Alkanes and aromatics are fairly stable compounds. To make them react, a special catalyst must be present. What catalyst must be present when reacting Cl2 with an alkane or with benzene? Adding Cl2 to alkyne does not require a special catalyst. Why are alkenes and alkynes more reactive than alkanes and aromatic compounds?

Short answer

Alkenes and alkynes are more reactive than alkanes and aromatic compounds because of AIkanes contain heat or light and aromatics contain strong Lewis acid.

Step-by-step solution

To find why are alkenes and alkynes more reactive

Alkanes can react with halogens, but heat or light is required to initiate halogenation.

On the other hand, alkenes do not need light or heat for the halogenation reaction because they are more reactive.

Alkenes are more reactive due to the double bond, i.e. sigma bonds are more stable than pi bonds. Double bonds are more electron-rich, which makes them potentially more reactive in the presence of a strong electron acceptor (as in addition reactions of the halogens).

And aromatic compounds undergo various reactions, but very few of them affect the pi bonds in the aromatic system.

Strong Lewis acids must be used for halogenation of aromatic compounds.

Hence Alkanes - heat or light; aromatics - strong Lewis’s acid.

Double and triple bonds are more electron rich.